1. Field of the Invention
The present invention relates to a heat sink unit for cooling a semiconductor device such as an IC and to an electronic apparatus.
2. Description of the Prior Art
Conventionally, a heat sink unit is used to cool a semiconductor producing a high temperature. Particularly, a fan-motor integrated heat sink unit having a high cooling effect in which a small fan is built in a heat sink is recently used in order to correspond to a high temperature produced by an MPU.
A conventional heat sink unit is described below. FIG. 6 is a perspective view showing a conventional heat sink unit. In FIG. 6, numeral 1 denotes a substrate and a plurality of semiconductor devices 2, 3, 4, 5, and 6 are set on the substrate 1. Numeral 7 denotes a heat sink unit which is set on a semiconductor device 6 producing a relatively large amount of heat. The heat sink unit 7 comprises a plurality of fins 8, a fan 9, and a motor 10 for rotating the fan 9.
An air flow is generated by rotating the fan 9 by the motor 10 and the semiconductor device 6 is prevented from being abnormally heated by applying the air flow to the fins 8. That is, the heat produced by the semiconductor device 6 is transmitted to the fins 8 and cooled by the air flow. Moreover, the air flow coming out of the heat sink 7 contacts the semiconductor devices 2, 3, 4, and 5 to cool the semiconductor devices 2, 3, 4, and 5.
However, the above conventional heat sink unit 7 has a limit in its cooling capacity. In addition to the heat produced by the semiconductor device 6 serving as a CPU, the amount of heat produced by the semiconductor devices 2, 3, 4, and 5 is increased because operation speeds of the semiconductor devices 2, 3, 4, and 5 are increased (clock acceleration) and a computer having two CPUs appears. Therefore, a problem occurs that adequate cooling cannot be made only by the air flow discharged from the heat sink unit 7.
Moreover, because electromagnetic waves are inevitably generated due to clock acceleration, a problem occurs that an action must be taken for electromagnetic waves in order to cut off unnecessary electromagnetic waves emitted from a lead 6a of the semiconductor device 6.